1. Field of the Invention
This invention relates to end-functionalized polymers, processes for, making the same, and polymers made using such end-functionalized polymers.
More particularly, the invention relates to a controlled free-radical polymerization process for forming end-functionalized polymers, particularly by a degenerative iodine transfer (DIT) and atom transfer radical polymerization (ATRP) processes.
The resultant end-functionalized polymers have a high degree of functionality, a polydispersity less than 2.5, and a predetermined molecular weight. The resultant end-functionalized polymers are useful as reactive intermediates in condensation polymerization, chain polymerization and heterogeneous polymerization reactions.
2. Description of the Prior Art
Controlled free-radical polymerization processes, including ATRP and DIT, are prior art processes for free-radical polymerization. In degenerative iodine transfer polymerization, chain growth is controlled by iodine atoms, which reversibly react with the growing polymer chain ends thereby, limiting side reactions. Iodine atoms are introduced into the reaction using iodine transfer reagents, and polymer radicals are initially generated with a small amount of a conventional initiator.
The atom transfer radical polymerization process can also produce products with more uniform and more highly controlled architecture. The process includes free-radical polymerization of one or more monomers, in the presence of an initiator having a transferable atom or group, and a transition metal compound with an appropriate ligand. The transition metal compound has the formula MLn, the ligand L being any N-, O-, P-, or S-containing compound, which can coordinate to the transition metal through a "sgr"-bond or any carbon-containing compound which can coordinate through a xcfx80-bond, such that direct bonds between the transition metal in growing polymer radicals are not formed. The formed copolymer is then isolated.
Application of the degenerative transfer process in the production of polymers is disclosed in the following references: Japanese Kokai No. 4-132706 (1992), assigned to Nippon Shokubai, discloses a DIT process for the production of telechelic polymers having hydroxyl groups at the ends. The initial formula of the reagent used is Xxe2x80x94Rxe2x80x94Xxe2x80x2 wherein X is bromine or iodine and R is a bivalent C1-C8 hydrocarbon. The reagents used in the method are not efficient, and thus require a great excess of the iodo reagents (0.01-10 moles monomer per mol of the reagent) to produce polymers having a molecular weight of 1500 and greater. Further, the molar ratio of halide reagent to conventional initiator is extremely high, being on the order of 50 to 500 to 1. The functionalization process for converting the chain-end iodides to a hydroxyl group is also inefficient. In this regard, four reactions are specified: (1) hydrolysis; (2) substitution with diols; (3) substitution with hydroxy amines; and (4) substitution with carboxylates. Reactions 1 and 2 promote side reaction with ester containing polymers whereas reactions 3 and 4 are often slow and incomplete. The molecular weights obtained by the method disclosed in Nippon Shokubai Japanese Kokai No. 4-132706 are for the most part high, that is, in excess of 5000.
U.S. Pat. No. 5,439,980 issued in 1995 to Daikin Industries discloses a DIT process wherein block copolymers are synthesized using an iodine reagent and two monomers, which are added simultaneously. The process relies on large reactivity differences between the monomers, and introduces no functional endgroups.
U.S. Pat. No. 5,455,319 issued in 1995 to Geon describes the use of DIT to produce vinyl chloride homopolymers and some random copolymers of vinyl chloride. The iodine transfer reagents employed in the ""319 Patent are efficient in that they are activated reagents. But the DIT polymerization process in an aqueous media is described only for vinyl chloride polymers and the patent does not address end-functional polymers.
K. Matyjaszewsky, in Macromolecules, Vol. 28, pages 2093-2095 and 8051-8056 (1995) describes a process for controlled polymerization using iodine compounds. Neither efficient difunctional transfer agents nor reagents having an incorporated functional group are disclosed.
Atom transfer radical polymerization (ATRP), on the other hand, is also described in the prior art. For example, WO 96/304212 to Matyjaszewski and Carnegie-Mellon University describes metal catalyzed free-radical polymerization using an alkyl halide initiator to control the polymerization.
The general idea of using a functionalized initiator for ATRP or functionalizing the halide end group from an ATRP polymer is mentioned in J-S Wang, D. Grezsta, K. Matyjaszewski, Polym. Mater. Sci. Eng., 73, 416 (1995). No examples are provided in the article, nor is it obvious how to carry out the hypothesis.
The synthesis of a polymer with an allyl end group using an allyl initiator or substitution with allyl trimethylsilane, and the synthesis of polystyrene with one amine end group using a trimethylsilyl azide reaction followed by hydrolysis are described in Y. Nakagawa, S. Gaynor, K. Matyjaszewaski, Polym. Prep., Am. Chem. Soc., Polym. Div., 37(1), 577 (1996).
A polymer with a vinyl acetate group formed using a functionalized initiator is described in K. L. Beers, S. G. Gaynor, K. Matyjaszewski, Polym. Prep., Am. Chem. Soc., Polym. Div., 37(1), 571 (1996).
Hydroxy end-functionalized polymers, and processes for making the same using non-living free-radical polymerizations, are also disclosed in prior art, European Patent No. EP 06223 78A 1 to Goldschmidt AG. This patent describes polymethacrylate diols and a process for making the same. The process is a conventional free-radical polymerization process initiated in the presence of a large amount of mercaptoethanol chain transfer agent. The polymer chain starts from mercaptoethanol and terminates with the methacrylate group, which is then converted to a hydroxyl containing moiety by a selective substitution reaction using an aliphatic diol in the presence of Ti(OR)4. The chain end substitution reaction specified is a moisture-sensitive and costly process. Furthermore, the reaction is only selective and efficient for methyl methacrylate polymers thus limiting the general applicability.
U.S. Pat. No. 5,391,655 issued in 1995 to Nippon Shokubai describes a process wherein vinyl monomers are polymerized by conventional free-radical polymerization in the presence of a great excess of a disulfide reagent containing two hydroxyl groups at each end. The formula of the disulfide reagent is HOxe2x80x94Rxe2x80x94Sxe2x80x94Sxe2x80x94Rxe2x80x2xe2x80x94OH and the molar concentration of disulfide reagent is greater than 50 times that of the initiator and at least 0.5 of the vinyl monomer. The process is flawed in that it cannot produce pure difunctional telechelics and in that large amounts of the functionalization reagents are needed.
Thus, there exists a need for a process capable of providing an end-functionalized polymers having a predictable molecular weight, high degree of functionality, and low polydispersity. The process must be sufficiently flexible to control molecular weight as well as polymer architecture. A living or controlled free-radical process followed by an efficient functionalization step provides a solution and is presented herein. Efficient iodine transfer agents or bromide initiators and inexpensive functionalization reagents are also needed.
The resultant end-functionalized polymers are useful as reactive intermediates for condensation polymerization of polyurethanes, polyesters and epoxides; chain polymerization to form graft copolymers and crosslinked copolymers; and polymeric emulsifiers.
The present invention provides a process for controlled free-radical polymerization followed by chain-end conversion for making end-functionalized polymers. Such polymers are also generally referred to as telechelic polymers. They are also known as macromonomers in the specific case where the end groups are unsaturated and polymerizable. Degenerative iodine transfer and atom transfer radical polymerization are particular examples of controlled free-radical polymerization. The polymers produced by these methods have a predictable molecular weight, halogen end-groups, and low polydispersity. The process disclosed herein includes both efficient transfer agents as well as efficient and minexpensive reagents. The process also describes the conversion of halogen end-groups to desired functional groups, using efficient reagents. The resultant end-functionalized polymers are useful as reactive intermediates in condensation polymerization, chain polymerization and heterogeneous polymerization reactions.
In the first aspect of this invention, a process for forming a polymer having at least one functionalized end group is disclosed. The process involves heating a mixture of an iodine reagent having at least one iodine end group, a free-radical initiator, and at least one polymerizable monomer. The molar ratio of the free-radical initiator to the reagent is about 10 to 0.001. The molar ratio of the polymerizable monomer to the reagent is about 10 to 1,000. The iodine end group is converted to the functionalized end group by reaction with a nucleophilic reagent.
According to a second aspect of the invention, a mono-end-functional polymer is disclosed, which has the formula:
R-polymer-Yxe2x80x94R2xe2x80x94Z1xe2x80x83xe2x80x83(I)
where R contains at least one radical stabilizing group and has at least 1-50 carbon atoms, the polymer and the radical stabilizing group are attached to the same carbon atom in R, and the radical stabilizing group is selected from the group consisting of an aryl, alkene, ester, acid, amide, ketone, nitrile, halogen, isocyanate, nitro and amine.
where R2 is a substituted or unsubstituted alkylidene group having 1-20 carbon atoms or is not present when Z1 is directly bonded to the polymer,
where Y is selected from the group consisting of oxygen, sulfur, and N(R5), where R5 is hydrogen or a substituted or unsubstituted alkyl group or is not present when Z1 is directly bonded to the polymer, and
where Z1 is selected from the group consisting of: OR1, N(R1)2, SR1, COOR1, COOM, olefin of the type xe2x80x94CR1xe2x95x90C(R1)2, epoxide of the type 
SO3M, PO(OR1)2, PO(R1)3, P(R1)3, xe2x80x94Nxe2x95x90Cxe2x95x90O and xe2x80x94CR1xe2x95x90O, wherein R1 is equal to H or a group having 1-20 carbon atoms, R1 being the same or different for any Z1 having more than one R1, and wherein M is a metal ion.
The term xe2x80x9cpolymerxe2x80x9d is used to define a molecular chain containing 5 to 500 monomer units, including mono- or disubstituted vinylic units, such as xe2x80x94[xe2x80x94CH(R6)xe2x80x94C(R4)(X)xe2x80x94]xe2x80x94 where R4 is selected from hydrogen, methyl, hydroxymethyl, phenyl, halogen, or CH2COOH, X is selected from the group consisting of an alkyl, aryl, nitrile, halide, alcohol, carboxyl, sulfonyl, ester of the type xe2x80x94COxe2x80x94Oxe2x80x94R3, acetate of the type xe2x80x94Oxe2x80x94COxe2x80x94R3, ether of the type xe2x80x94Oxe2x80x94R3, carboxyamide of the type xe2x80x94COxe2x80x94N(R3)2 and amine of the type N(R3)2, wherein R3 is equal to H or a group having 1-30 carbon atoms, R3 being the same or different for any X having more than one R3, where R6 is selected from hydrogen, methyl, phenyl, halogen, or CH2COOH, alkyl, aryl, nitrile, halide, alcohol, carboxyl, sulfonyl, ester of the type xe2x80x94COxe2x80x94Oxe2x80x94R3, acetate of the type xe2x80x94Oxe2x80x94COxe2x80x94R3, ether of the type xe2x80x94Oxe2x80x94R3, carboxyamide of the type xe2x80x94COxe2x80x94N(R3)2 and amine of the type N(R3)2, or diene monomer units. The polymer chain may be composed of a series of one monomer or a random mixture of two or more of these monomers. In addition, the chain may have a non-random distribution of the monomers, such as when the distributions are a diblock, triblock, multi-block, or graft structures. The polymer is formed in the DIT or ATRP process and is preferably poly (n-butyl acrylate), polystyrene, poly(ethyl acrylate), poly(ethylhexyl acrylate), or poly(acrylonitrile-co-n-butyl acrylate).
According to a third aspect of the invention, a bis-end-functional polymer is disclosed, which has the formula:
Z2xe2x80x94R-polymer-Yxe2x80x94R2xe2x80x94Z1xe2x80x83xe2x80x83(II)
where R, Y, R2, and Z1 are as previously noted, Z2 is selected from the same group as Z1, and Z1 and Z2 are independently selected.
According to a fourth aspect of the invention, a bis end-functional polymer is disclosed, which has the formula:
Z1xe2x80x94R2xe2x80x94Y-polymer-R-polymer-Yxe2x80x94R2xe2x80x94Z1xe2x80x83xe2x80x83(III)
where R, Y, R2, and Z2 are selected as previously noted.
According to the fifth aspect of the invention, ATRP can be used to form a prepolymer with bromide or chloride end groups, which can be functionalized by conversion of end group by reaction with a nucleophilic reagent.
One advantage of the present invention is that the degenerative iodine transfer process disclosed employs efficient chain transfer agents.
Another advantage of the present invention is that the degenerative iodine transfer process disclosed provides both molecular weight and polymer architecture control.
Still another advantage of the present invention is that a degenerative iodine transfer process is disclosed wherein inexpensive iodine reagents, in amounts much less than those specified in the prior art, are disclosed.
Another advantage of the present invention is that a degenerative iodine transfer process disclosed is effective with a wide variety of monomersxe2x80x94that is, more than fluorinated monomers, can be used in the practice of the DIT process.
Still another advantage of the process disclosed is the efficient end-group conversion applied to polymers prepared by ATRP.
Another advantage is that the resulting end-functionalized polymers, or telechelic polymers, can be used in a condensation, radical, anionic, or graft polymerization processes.
Still another advantage is that using the described process a wide variety of monomers can be used.
Another advantage is that a wide variety of functional end groups can be introduced with the appropriate choice of nucleophilic reagents.
Still another advantage is that the iodine can be recycled in the described process.
Another advantage is that the efficient iodine transfer reagents can contain one functional group and only one iodine which lowers the amount of iodine used in the process compared to bis iodine reagents.
Still another advantage is that polyacrylate diol polymers can be made which improve properties and give higher hydrolytic and UV stability when incorporated in polyurethanes, polyesters, polyamides, polycarbonates, and polyepoxides.
Another advantage is that olefinic end-functional polymers, also known as macromonomers, can be produced which can be used to prepare graft copolymers in chain polymerization to form block and graft copolymers.
Still another advantage is that polymers can be formed with ionic end groups, useful as polymeric surfactants.
Another advantage is that polymers can be formed with two different functional end groups.
Still another advantage is that end-functional diblock or triblock copolymers can be made.
Still other benefits and advantages of the invention will become apparent to those skilled in the art upon reading and understanding of the following detailed specification.